Density and structural distributions in artificial graphites

Densitometric separations were performed on a number of artificial graphites, and the apparent crystallite sizes of the density fractions were measured. Anisotropic porous artificial graphites are shown to consist of semigraphitic regions coexisting with highly graphitic regions. The transition of the structure from semigraphitic to highly graphitic is smooth, and the apparent crystallite size can be correlated with the apparent density of the fractions. The near-isotropic graphites have semigraphitic structures and are more uniform in apparent crystallite size than the anisotropic graphites. The mean apparent crystallite size L̄c of the graphites shows a systematic correlation with the volume thermal expansivity of the samples. Materials that are nearly isotropic, such as Poco or Gilsonite graphites, have the highest thermal expansivities, the smallest apparent crystallite sizes, and the smallest range of crystallite sizes.